We've got two numbers: 2790 and 78. Let's find their sum.

Step 1: We'll start by adding the digits 0 & 8 in column 1 and get 8.

Step 2: We'll start by adding the digits 9 & 7 in column 2 and get 16.
We'll write down the last digit 6 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 7 & 0 in column 3 and get 8.

Step 4: We'll start by adding the digits 2 & 0 in column 4 and get 2.

So, 2790 + 78 = 2868.

